application of conic sections

...French engineer Girard Desargues initiated the study of those properties of conics that are invariant under projections (
see projective geometry). Eighteenth-century architects created a fad for whispering galleries—such as in the U.S. Capital and in St. Paul’s Cathedral in London—in which a whisper at one focus of an ellipsoid (an ellipse rotated about one axis) can be heard at...

reflection of sound

...from which sound is to be observed and then focus it onto a microphone. An elliptical shape, on the other hand, can be used to focus sound from one point onto another—an arrangement called a
whispering chamber. Domes in cathedrals and capitols closely approximate the shape of an ellipse, so that such buildings often possess focal points and function as a type of
whispering chamber....